Correlation between hardness and embedded argon content of magnetron sputtered chromium films

Chromium films were produced on steel substrates by d.c. magnetron sputteri ng in pure argon at a target power density of 2, 4, 10 or 16 W/cm applying a negative substrate bias voltage, V-s, ranging from 4 to 1000 V. The subst rate temperature varied from 158 to 600 degrees C. Some experiments were co nducted at a constant temperature of 600 degrees C. The film hardness was m easured by Vickers microindentation. Gas content in the films was analyzed by electron probe microanalysis. The film microstructure was investigated b y X-ray diffraction and transmission electron microscopy. At constant depos ition rate, while increasing the substrate bias, first the film hardness re mained constant and beyond a threshold bias value increased from 4 to 11.7 GPa. The threshold bias value increased with the target power density. The temperature series performed at V-s = 500 V and a target power density of 4 W/cm(2) revealed that the film hardness decreased from 12 GPa to 8 GPa whe n increasing the substrate temperature from 300 to 600 degrees C. The micro structure of the films was found to vary with the deposition parameters. Ho wever, over the results for all the experiments performed here, a clear rel ationship has been established between the microhardness and the argon cont ent of the films. Furthermore, a relationship between the argon content and the deposition rate was established for the films produced at V-s 500 V an d T-s = 600 degrees C. (C) 1999 Elsevier Science S.A. All rights reserved.